Autodesk recently announced Maya 2017 that has a lot of new features and large numbers of improvements and several bug fixes and the biggest changes is also switching to Arnold renderer which is set to be the default render.
It is also set to be faster and more efficient than Mental ray
Mental ray can still be installed as a 3d party plugin, if not may cause issues with files saved in older builds of Maya and may even crash it.
While some may like the new renderer for others it is an extra plugin they need to install to get their favorite render back.
An article will be published sooner that will reveal more details of the change in Maya so stay tuned.
Keep rendering awesome stuff,
Thank you for reading.